Tooth crown construction and process for forming the same



Dec. 16, 1969 v. ANDREW 3,483,618

TOOTH CROWN CONSTRUCTION AND PROCESS FOR FORMING THE SAME Filed July 2, 1963 INVENTOR VLADIMIR ANDRELU By fin /Mud Tm nited States Patent 3 483 618 TOGTH CROWN CONSTR UCTION AND PROCESS FOR FORMTNG THE SAME Vladimir Andrew, 3 Bld. dAnvers, Strasbourg, France Filed July 2, 1963, Ser. No. 292,417 Int. Cl. A61c 5/08, 5/10 US. Cl. 32-12 Claims This invention relates in general to tooth crown construction and to a process for making a dental crown, and in particular to a new and useful tooth crown employing a metal hood or cap which is fitted over the stump of a tooth to which is solidly connected a shell member on the lingual or pallatine side which member is arranged in spaced relationship with the hood for receiving the extended portion of a facing layer applied to the vestibular side of the crown, and to an improved process for making such dental crowns.

At the present time crowns consist of a hood sealed on the stump of the tooth and are made of metallic material, preferably gold, and of a part of material which simulates or approaches the natural color of the tooth. The tooth simulating material covers the front, i.e. the labial or the vestibular face, of the hood. \Nith prior art constructions this material, such as porcelain is usually held in place either by means of a small flange of the metal part of the crown which it is suitably crimped, or by metal clamps, or projections, which grip the edge of the material or which anchor the porcelain itself, such as by adhesives. All of these known forms of crows with facings have the drawback that the anchorage elements for the porcelain material either remain visible or are not strong enough. In the latter case there is the risk that there will be an infiltration of buccal liquid between the metal part of the crown and the porcelain layer resulting in a discoloration or even an ungluing of the latter.

In applicants patent application Ser. No. 115,585, filed Apr. 11, 1961, and now Patent No. 3,273,242, issued Sept. 26, 1966, there are set forth the details of a crown which is formed with a double wall and only the interior wall is sealed to the stump of the tooth to be crowned, while the outer wall extends upwardly on the rear portion of the tooth in spaced relationship to the inner wall which covers the stump. The coating layer or porcelain facing which simulates the tooth may then easily be joined to the front of the crown and to the upper portion of the exterior wall which is spaced from the interior wall top, with portions thereof extending into the space between the interior and exterior walls.

A construction of this nature not only guarantees a solid anchorage of the crown and the porcelain layer to the hood, but insures that no infiltration of the buccal acid will occur between the metal inner wall of the hood and the coating or porcelain layer.

The present invention is an improvement over applicants previously filed application, particularly in respect to the use of shell elements of standard size which are easily assembled and then connected to the hood and thus greatly facilitate the construction of the crown.

In the manufacture of the crown set forth in applicants copending application mentioned above, the procedure is as follows:

From the impression of the stump prepared in the mouth of the patient a model of the stump is made on which is reconstituted the tooth in wax including the exterior form thereof. From the reconstitution of the tooth a matrix of plaster is made which encompasses all of the outer faces of the metal part of the future crown. The matrix is then axially cut in two halves, and then the wax having the outer form of the future crown is removed from the stump. On top of the stump is fashioned by the application of a calibrated wax, the model of the in ner wall in the form of a hood. Then the model of the outer metal wall is united by adapting to the interior of the matrix at points corresponding to this part a wax Of a suitable thickness. Then the stump, covered with the hood, is returned to the matrix. First one half is removed from the matrix in order to connect on one side the outer and inner walls of the model, and then the other side is removed to perform the same step. The model thus obtained of the metal part of the crown is removed from the stump and is ready for casting which is carried out in a known manner.

In accordance with the present invention the above process is vastly simplified. A model of the stump is prepared in the usual fashion from the impression taken in the mouth of the patient. On the stump there is applied a hood, preferably of wax or some other suitable material. This hood constitutes the inner wall of the future metal part of the crown. In accordance with the invention, an outer wall corresponding to the crown is secured to the inner wall. This outer wall consists of a shell which is prefabricated of wax or some other suitable material. To this end, the shells are made up in a whole series of sizes, and the forms are numbered, for example, so that it is a simple matter to provide a stock of shells to take out the shell shape and color selected.

The outer wall of such crown shell always comprises all of the faces of the tooth which are not visible in the mouth, and the coating or facing layer is reserved for location at the visible face of the tooth. The shell is connected to the hood in such a way as to leave a pocket-shaped space between the shell and the hood wall for receiving part of the coating layer which will be applied to the front face of the hood so that the coating layer is anchored securely thereat.

To increase the strength of the crown, particularly to maintain the distance between the two walls as Well as to insure the anchoring of the facing or coating material, it is also possible to provide pins or rods, preferably made of small bits of wire with a melting point higher than the melting point of the alloy designed for the casting of the crown. These pins can be inserted into the inner wall and the exterior wall or shell when the model is being made, or they can already form a part of the prefabricated shells. After the shell is solidly connected to the hood, the model of the crown part is ready for casting. and this is carried out in the usual manner.

The shells which constitute an essential part of the invention are prefabricated in a certain number of standard forms and sizes, for example, in series of several sizes for each tooth. They can be made either of wax or some other suitable calcinable material, that is a material capable of volatilizing when the mold is heated after being placed around the model of the crown. The shells may also be provided with metal pins or rods which are offset with respect to the shells and extend outwardly therefrom and serve to guarantee good proportioning of the pocket-shaped space formation between the crown inner wall and the shell and also insure retention of the extension or prolongation of the coating material between the two walls determined by the hood and shell. Such rods are constituted by bits of wire which respond to the condition mentioned above. The shell can finally be made of a metallic material such as gold and be connected, for example by welding, directly to the hood. The shell can be cast separately and provided with retaining rods, or it can be fitted with such rods as it is being made.

Accordingly, it is an object of this invention to provide an improved process for making a tooth crown.

A further object of the invention is to provide an improved tooth crown construction.

A further object of the invention is to provide a process for making a dental crown with a facing and, with two walls spaced apart to leave a space or interstice into which extends the facing forming coating material applied to the visible surface of the crown, characterized in that over the model of the stump of the tooth, which is obtained in the usual way from an impression taken in the mouth, a hood is applied, in wax or some other suitable material, which indicates the inner wall of the metal part of the crown, and then a piece in the form of a shell, prefabricated of wax or some other suitable material, is positioned upon and connected to the hood, the shell forming the model of the outer wall of the future metal part of the crown and being arranged in a way so as to define said space between the shell and the hood for permitting a coating material to extend into and to be anchored in this space.

A further object of the invention is to provide a process for forming a dental crown, characterized in that the hood is formed on the stump of the tooth and then cast, and the outer wall of the metal part of the crown is constituted by a shell prefabricated of metal which is positioned on the hood and welded spacedly connected thereto.

A further object of the invention is to provide a process for making a dental crown which is simple in concept and execution and economical to carry out.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings, and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a perspective view of a shell looking into the interior thereof and used in accordance with the process of the present invention;

FIG. 2 is a view of the same shell as seen from the front or vestibular side;

FIG. 3 as seen in the direction of the arrows is a section taken on the line 3-3 of FIG. 2;

FIG. 4 is a bottom plan view of the shell indicated in FIGS. 1-3;

FIG. 5 is a partial elevation and partial section of a model of a tooth stump covered by the metal part of the crown, the latter being shown in longitudinal section; and,

FIG. 6 is a front view of the model of the crown indicated in FIG. 5 which has been removed from the stump.

Referring to the drawings in particular, the invention embodied therein indicates in FIGS. 1-4 the shell 3 which is to be employed in the process of the invention. The

shell 3 is indicated to be designed for the crown of an incisor. It is understood that prefabricated shells can have the various shapes necessary for the fabrication or confection of crowns designed in respect to the various teeth of a person. It is likewise understood that these various shapes are made in series with staged dimensions. The shell 3 can consist either of wax or any other natural or artificial material capable of volatilizing when the casting mold is heated after it is confectioned around the model of the metal part of the crown. In addition, the shells may :be provided, when made, with spacing and retention rods which are not shown in FIGS. 1 to 4.

In FIG. 5 there is indicated the upper part of a model of a stump 1 made from the impression taken in the mouth of a patient and covered with a model of the crown. In FIG. 5 the model of the crown is shown in section, and this model is confectioned according to the invention by the following process:

After the stump 1 is prepared, an inner wall of the crown is formed by applying on the surface of the stump, for example, calibrated wax to form a hood or cap 2. After the hood 2 is formed, a determination of the dimensions of the shell to be apposed to the hood is determined. To do this, a set of forms, for example numbered forms having various sizes and the various shapes of prefabricated shells, is previously made up. When the correct form is located, then the correct shell is selected from a stock of shells matching the form. The shell 3 is then directly apposed on the lingual or palatinal side to the edge of the hood 2 and solidly connected to the latter, for example by a joint 4 of wax. The shell 3 should be disposed in such a way as to leave between it and the surface of hood 2 a pocket-shaped space 5. In certain cases one can apply a second joint 6, somewhat higher than the location of wax connection 4 in order to reduce the space defined between the shell 3 forming the outer wall and the hood surface 2 forming the inner wall. This second joint 6 is not indispensable, however.

The end edges of the shell are marked :by the dotted line 6a. The inner lower end of the hood or cap .1. that is the labial or front side, is provided with a flange 8 which terminates flush with the root 1 of the tooth.

The dash line 9a which extends from the peak of the outer Wall or shell 3 to the outer edge of the flange 8 on the vestibular side indicates the front face of the facing material 9 which will be applied after casting. The facing is applied to the metal part of the crown on the visible side in the mouth and extends into the space or pocket 5. The facing 9 is anchored on the one hand inside the space 5 by the retention rods 11 indicated in FIG. 6, and at the upper portion of FIG. 5. Upstanding projections or prong elements 7 formed on the labial face of the hood 2 also insure improved anchorage of the facing 9.

A variation of the process set forth above consists in preparing only the model of the hood 2 which is cast in such a way as to obtain just the hood of a metal, such as gold. Then there is attached to the hood 2, by welding, a shell 3 which represents the outer wall of the metal part of the crown. This shell 3 in this instance is already prefabricated of a metallic material, for example gold. When the selected shell is welded to the hood in this manner. care must be taken to leave sufficient space between the two walls thus obtained. Before placing the shell over the hood, the retention rods are welded on the hood. In some instances the rods may be formed integrally on and offset with respect to the inner face of the shell and may merely rest on the surface of the hood 2.

The drawing only indicates one particular form of a mold and crown confectioned according to the invention which is selected as an example. It should be appreciated that variations may be made in accordance with the invention without departing from the principles thereof.

What is claimed is:

1. A tooth crown construction comprising a die formed over the stump of a tooth, including a front wall portion adapted to face outwardly and be visible in the mouth, and a back wall portion adapted to overlie the rear portion of the tooth and be invisible in the mouth, a prefabricated shell portion extending upwardly from the rear portion of the die and being connected at its lower periphery to said rear portion, said shell portion being spaced from the upper end of said die and from said back wall portion for accommodating a coating in the space between said shell portion and said back wall portion, said coating being applied over the front wall portion of said die, and bits of wires in the space between said die and said shell.

2. A process of forming a dental crown having .1 double wall, whose inner wall is adapted to overlie the tooth to be provided with the crown and whose outer wall is spaced from said inner wall and located on the inner side of and not visible from without the patients mouth; comprising the steps of preparing a model of the stump of the tooth by taking an impression thereof within the patients mouth, fitting a hood of volatilable material over the resultant tooth stump model to constitute the model of the inner wall of the crown, applying against said hood at the lingual side thereof a shell of predetermined size and material to correspond to the particular tooth for forming the model of the outer wall of the crown, and connecting the lower shell portion to the hood in such a way as to leave the remaining portion of the shell including its top spaced from said hood, thereby to obtain a pocket-shaped formation between said shell and said hood at said lingual side preparatory to crown casting.

3. A process according to claim 2, including the step of inserting retention pins into said shell and hood for location there between before the shell is connected to said hood.

4. A process according to claim 2 including the step of roughing the labial side of said hood for improving anchorage of facing material thereat.

5. A process according to claim 2, including the step of preparing a flange at the lower portion of the hood opposite the lower portion of said shell for facilitating support of facing material thereat.

6. A process according to claim 2, wherein the hood is formed directly on the stump of the tooth and then cast and the outer wall of the metal part of the crown is made by a shell prefabricated of metal and welded to the hood.

7. A process of manufacturing a dental crown having a double wall formation, of which the inner wall is adapted to overlie the upper end of a tooth stump, while the outer wall is connected to a portion of the inner wall not visible from without the patients mouth; comprising the steps of fitting a cap-shaped element of metal, which constitutes the inner wall, onto the tooth stump, preparing a flange at the lower portion of said element adjacent the labial side thereof, and connecting at the lingual side a prefabricated and the outer wall forming shell of metal at its lower portion to said element, while spacing the remaining portion of said hell above and relative to the remaining portion of said element, so as to provide a pocket-shaped formation tapering from the top of the shell toward said lower shell portion and between said inner and outer walls at said lingual side.

8. A process according to claim 7, including the step of applying a facing forming layer to said flange, and extending said layer over said element at its labial side into said pocket-shaped formation for positioning said facing.

9. A process according to claim 8, including the further step of retaining said layer in position by offsetting portions with respect to said inner wall and said outer wall, which are not visible from without the patients mouth.

10. A process according to claim 8, including the further step of offsetting confronting parts of said inner wall and said outer wall for facilitating anchorage of said facing layer thereat.

References Cited UNITED STATES PATENTS 1,609,549 12/1926 .laques 32-12 2,930,125 12/1958 Pos 3212 1,425,055 8/1922 Rose 3212 2,744,326 5/1956 Chaiken et al. 32-12 3,052,983 9/1962 Weinstein et al. 3212 1,5 82,294 4/ 1926 Montuori.

FOREIGN PATENTS 855,307 11/1952 Germany.

ROBERT PESHOCK, Primary Examiner 

1. A TOOTH CROWN CONSTRUCTION COMPRISING A DIE FORMED OVER THE STUMP OF A TOOTH, INCLUDING A FRONT WALL PORTION ADAPTED TO FACE OUTWARDLY AND BE VISIBLE IN THE MOUTH, AND A BACK WALL PORTION ADAPTED TO OVERLIE THE REAR PORTION OF THE TOOTH AND BE INVISIBLE IN THE MOUTH, A PREFABRICATED SHELL PORTION EXTENDING UPWARDLY FROM THE REAR PORTION OF THE DIE AND BEING CONNECTED AT ITS LOWER PERIPHERY TO SAID REAR PORTION, SAID SHELL PORTION BEING SPACED FROM THE UPPER END OF SAID DIE AND FROM SAID BACK WALL PORTION FOR ACCOMMONDATING A COATING IN THE SPACE BETWEEN SAID SHELL PORTION AND SAID BACK WALL PORTION, SAID COATING BEING APPLIED OVER THE FRONT WALL PORTION OF SAID DIE, AND BITS OF WIRES IN THE SPACE BETWEEN SAID DIE AND SAID SHELL. 